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DBMDL

A library for modelling databases according to a Go struct. Intentionally made lightweight, for this library is not meant to replace SQL languages in your project.

Basic usage

Structs can be externed with dbmdl tags. This tag must always start with the datatype (e.g. char(15)) or an extern field.

Datatype

When a datatype is provided, DBMDL can modify a linked table in the database. In most cases, the programmer would enter a datatype. The amount of available datatypes depends on the implementation of the SQL driver that is used.

Syntax: dbmdl:"DataType, Parameter1, Parameter2"

Parameters
  • primary key: Indicates that the field is a primary key in the database. There may be multiple primary keys.
  • default X: Specifies a default value in the database. X indicates some default value.
  • not null: The value may not be NULL. Note that it is preferred to use this, rather than appending not null to the database.
  • omit: Omits the value by default when performing a Population. Useful for columns with optional fields or expensive fields that don't always need to be loaded

Select field

The select field is used only for loading a struct. It adds a field to the selection statement.

Syntax: dbmdl:"select" dbmdl_field:"<Selectable>"

Extern field

The extern field is used only for loading a struct. It loads data from an specified table using a JOIN-clause. This is used for when structs need to be linked with data in other tables.

Syntax: dbmdl:"extern" dbmdl_field:"<ExternField>" dbmdl_table="<ExternTable>" dbmdl_condition="<Condition>".

Where:

  • ExternField is a field name of a table that is not our the struct's table
  • Table is the name of said table
  • Condition is a joining condition, e.g. table_one.LocalField2=table_two.ExternField2

The join type is always INNER, unless a dbmdl_join tag is defined.

Example

// Package database
package database

import (
	"github.com/kurt-stolle/go-dbmdl/postgres"
	"database/sql"
)

var Dialect = new(postgres.Dialect)

func Open() *sql.DB {
	return sql.Open(...)	
}	

// Package models
package models

import "github.com/kurt-stolle/go-dbmdl"

type User struct {
    UserID      string          `dbmdl:"uuid, primary key"`
    FirstName   sql.NullString  `dbmdl:"varchar(50)"`
    LastName    string          `dbmdl:"varchar(50), default 'Undefined'"`
    Password    string          `dbmdl:"varchar(255), not null, omit"`
    
    NonDBMDLValue int
    
    privateValue bool
}

var UserModel = dbmdl.NewModel("users", reflect.TypeOf((*User)(nil)), database.Dialect, database.Open)

type Keys struct {
    KeyID           string `dbmdl:"uuid, primary key"`
    LinkedUserID    string `dbmdl:"uuid references users(UserID) on delete cascade, not null"`
    UserLastName    string `dbmdl:"extern users.LastName from users on keys.LinkedUserID=users.UserID"`
}

var KeysModel = dbmdl.NewModel("keys", reflect.TypeOf((*Key)(nil)), database.Dialect, database.Open)

Documentation

See godoc.